In recent years, a demand for optical glasses having high-refractivity and high-dispersion properties is increasing year after year. As such a glass, there is known an optical glass having a phosphate-based glass composition as a base material and containing a relatively large amount of components that give a high refractive index, such as TiO2 and the like (for example, see JP-A-6-345481).
However, the above glass contains a relatively large amount of components that give a high refractive index such as TiO2 and the like while having a phosphate-based glass composition as a base, and as a result, the glass is liable to be colored and has a problem from the viewpoint of a color degree. In the invention of the above JP-A-6-345481, attempts are made to heat-treat the optical glass for improving the glass with regard to the coloring. In this case, however, a heat-treatment step is required, and the procedure therefore inevitably comes to be complicated. Further, there is another problem that it is difficult to impart the entire glass with a uniform color degree.